btw., during the past decade we have had countless very ugly driver DMA bugs in the past that took vendors months and specialized equipment to track down.

I cannot give you a number breakdown, only an impression: storage drivers tended to be the hardest hit (due to the severity of the bugs and due to their inherent complexity) - but DMA bugs in networking drivers can be hard to track down too.

Plus there's another benefit: if a driver passes this checking and there's still DMA related corruption observed, then the hardware / firmware becomes a stronger suspect. This helps debugging too.